Alright, my problem is how do you export a mixed down 5.1 surround sound file? It only lets me export each track but I want it all in one. mixing down the tracks to their respective 5.1 channels doesn't improve the sound quality, it simply is part of the conversion process to eventaully burn all five mono channel onto a dvd if you have sonic foundry's 5.1 plugin. if you leave the song in 5.1( and without rendering to any other form) go to tools > burn track at once > close disc when done burning. acid will automatically burn in stereo, but your panning to the left,rightfront and back will remain exactly where you left them in the mix. it works great trust me sounds way better than changing to stereo or rendering to another file format. In regards to your other problem with doubling the guitar to make a heavier sound,reverb, delay or pitch shifting will only alter your sound they can't make it naturally fuller. the best solution is to play and record the tracks two different times. the slight variations between the two tracks ( such as different picking or strumming or an eq. adjustment) will make it sound like two guitarists playing the same riff rather than one track doubled.Also be sure to pan them to the hard left and right to get the fullest sound, maybe even double both of these tracks but put them closer to the center with a touch of reverb on the doubled tracks good luck!!!